Citation

Perminov NA. Аpplication of
Electroosmosis and Monitoring for the
Management of Geotechnical Processes in
Underground Construction. J Water Technol
Treat Methods. 2018;1(1): 104

Abstract

A new concept for the selection of rational construction and engineering parameters
for the building of large deep-set edifices is set out for an environment where the
requirements on preservation of historical sites and rational usage of land in big cities and
growing more taxing. Based on the proposed geotechnical model, and the assessment of
the results of quantitative modelling, research and experiments, a number of techniques
have been developed intended to optimise the technological modes of construction
under adverse urban conditions involving hard-to-handel soils and constrained urban
ambience.

Application of Geotechnics and Monitoring in solving problems of construction of unique underground structures in difficult conditions

Today the problem of working out the complex measures providing high quality
building turns out to be very actual. It could be explained by growing demands towards
ecology, earth resources and environment protection against negative technogenic
influence Geo monitoring systems rank among such measures.

The experience in design and construction of sewage treatment systems and
constructions had proved such systems necessity. It is well known that for such purposes
main pump stations are usually build with dipping method.

Today St. Petersburg and many large cities all over the world are facing the problem
of metro construction connected with the lack of free territory. In connection with it we
propose to build junction metro stations of St-Petersburg metro in large-sized dipping
wells (Figure 1)

Figure 1

We propose to use a construction with 66.0 meters in diameter and 70.0 meters high
for that purpose. It will allow organising the junction terminal in the lower part of the
well. The upper part could be used for a 7-stored underground garage for 850 cars. Due
to that we would save 15000 square meters of the city territory. Usually the constructions
of the described type are deepen into the ground for 70 meters. Their cross section ranges
from 2000 to 3000 sq. meters. So the contacting area between their lateral surface and the
ground is from 150 to 200 thousands of sq. meters. When being used these constructions
cross several (above 5) aquifer levels and greatly influence upon the surrounding buildings
and geologic environment.

The type and the after-effect of such influence differ from time to time. On one hand they
arc determined by the engineering and geological conditions of the construction site. On the
other hand - by the designing and technological peculiarities of the deepen constrution and
it’s building. Hence there is a problem how to exclude or minimise the above mentioned
negative after-effect. To be settled this problem needs the systematic approach towards
joint solving of geotechnical and engineering problems.

Today we are undertaking the works upon geo- monitoring system creation. This system
is being implemented step by step in Northern and Southern sewage systems construction.

The geo-monitoring system structure is based on the following subsystems [1,2,3,4]:

the program system calculating and forecasting the changes in technical and geological
conditions and Strained and Deformed State (SDS) of geological block under different
building modes for dipping constructions;

the technical tools subsystem for instrument observations and monitoring of
“construction - geo block” system elements;

informational and measuring subsystem for gathering, processing storing and
identification of observation and monitoring data;

the system of geo-technological methods for determinated operation upon ground
block and construction;

automation and optimum control subsystem for geo-technological
and other processes.

We have large experience in implementing of different methods
providing reliability and quality in deeping constructions building.
Our experience shows that geo-monitoring system should be adapted
to control the processes in semi-continuous mode and in real time.

Some research institutes had used strained and deformed state
control system for deeping wells construction. The results shoe
that every deviation from the project is registered by the control
instruments.

However it’s a great problem to use this data for determinated
process control. It is explained by the fact that it takes much time from
the moment of getting the initial data to the moment of it’s analysis
and issuing the recommendations for some technological steps. It is
connected with the long period of time needed for data processing.
Unfortunately the structural and geo - engineering conditions also
change meanwhile.

Our investigations gad shown that it’s possible to provide the
reliability and uniformity for edifices deeping process. It could be
achieved by creating the semi-continuous interaction system for the
three- dimensional (dX, dY, dZ) and time (dt) process variables [5,6].

We have taken out some estimate-theoretical and research
works. As a result we have worked out and tested the complex system
providing the geo- technical support for deep-set edifices deeping
process. These edifices were from 50 to 70 meters in diameter. They
had been implemented in waste treatment facilities construction in
St. Petersburg.

The mentioned above system comprises three following
complexes: measuring-control complex; signal estimation and
transmission for process control purposes; immediate feed-back
complex.

The results of reinforcement strain and distortion detection were
used to estimate the Edifice shell SDS. String detectors and strain
sensors that were stacked to the reinforce were used for that purpose.

Edifice bank was detected by the bank sensors. Those sensors are
based on double string gauging transformers (measuring accuracy
didn’t exceed 10 sec).

Geo mass SDS and well orientation forecast is worked out on
base of the above mentioned calculations. Besides we can build a
model of edifice vertical angular deviation.

We can forecast the location of deeping marks with the damage
emergency. On base of such forecasts we can select the most
acceptable geo- technical methods for geomass SDS measuring
not only at the edifice base but also in the lateral surface. Besides
we can select the methods to change the conditions for their
contact interaction.

We can make the techno-echonomical estimation and select the
optimum method to provide deeping process reliability and
acceleration.

We had fulfilled several cycle calculations with Finite elements
method for the ground conditions typical for St. Petersburg
(Quaternary sediments 26 - 35 meters deep, underlayed by hard
Cambrian clays).

As a result of computing experiment we had calculated the
admissible deviation ‘dh’ from the vertical axes and non-deforming
fits ‘di’ values. We have come to a conclusion that tixothropic jacket
is the best possible solution in this case. It results in friction strength
decrease on the marks from 16 to 47 meters. Hovering stability is
achieved through electroosmosis up to 16 meters height and with
‘di’< 0.015. We propose dedicated method for geomass preparation to
correct the bank for ‘h’ and di high values. Besides, what we propose
is the discharge well design in knife and lateral surface areas.

The described above results of using geomonitoring system for
large diameter deep-set edifices construction could be successfully implemented for large scale basements construction. Besides it might
be used for deep-set edifices construction in hard and complicated
ground conditions. Also this method could be used for developing
and reconstruction of existing underground territories in large cities.

Structural and Geo-technological model for large
scale deep-set edifices construction in under city
building system conditions.

To save city building environment we have worked out the
structural geo-technological model of large scale edifice construction.
This model is created considering the characteristic features of
interaction between structural and technological processes on one
side and engineering and geological processes on the other.

Being the monitoring object the deep-set edifice is represented
as a Geo-Technical System (GTS) - that is the interconnected
and interlined assembly of Technical Object (TO) (the deep-set
construction itself) and of geological object (GO) (the ground)
[11,12].

Technical object is a steric one with the concentrated influence
and distributed structural and technological parameters. Geologic
object is an assembly of city building and geomechanical elements
that might be combined corresponding to geological environment
model.

GTS is influenced by a great number of factors that could be
divided into three following groups:

construction elements mass (G);

geological environment reaction (X);

and external (artificial and natural) disturbance (H).

Each vector: G, H, X, consists of numerous factors. The greater part
of those factors is unknown. To determine them multidimensional
distribution law for probability distribution should be defined [13].

Please find bellow the equation that describes the process
of deep-set edifice construction and functioning. This equation
describes it in a simplified mode according to the common principals.

The task for optimum GTS monitoring could be formulated
in the following way: one is to find the control rules U(t) for GTS
taking into consideration a set of regulations. These regulations
transfer technological and geological objects to the monitoring mode.
Optimum function should have an extreme and is expressed with the
following equation [14]

where P is continuous function of output variable Y and of
controlling influences H, G, U.

Optimum criteria for the whole period of GTS development and
functioning (e.g.: deep-set well construction) is represented as a sum optimum criteria elements on each construction stage (installation
and deeping).

Optimum GTS control is reduced to the step by stem To and GO
variables control. The control is fulfilled according to the algorithm of
optimum way of aim achievement. So our aim is to settle the problem
of deeping the well shell under the optimal geo-technological
conditions in the preset time or with the minimum influence upon
city building environment.

Geo-technical research and manufacturing results

Geo-technical research works include large scale laboratory
experiments, quantitative modelling by Finite elements method and
site testing.

To simulate the conditions of deeping by Finite elements method
we had used incremental ground model, based on generalised Gook
principle. The relation between strain and deformation increments
was computed separately for stress tensor deviation and spherical
components [15].

First in laboratory and then on the site we have carried out the
investigation to find out the tixothropic solution features influence
upon the large scale deep-set edifices deeping process. The plan of
monitoring instruments location is shown in Figure 2.

Figure 3

Engineering and geological conditions of the construction site are
typical for St. Petersburg city building environment. It means that the
territory is formed by the grounds of Quaternary sediments 26 - 35
meters deep, underlayed by semi hard and hard Cambrian clays up to
the 71.0 meter depth.

The well for Northern waste treatment facilities with 66.1
meter diameter is designed as a monolith unite. We had included a
tixothropic jacket into construction to provide the deeping process reliability. Deeping process quantitative modelling for large scale
wells in the inclined layers of Cambrian clays had shown the
necessity of control system for deeping process. The system included
electroosmosis plant and instrumental control net [1,4,16].

Electroosmosis plant comprised the electrode bell 10.5 meters
high mounted on the knife external surface and 45 tube electrodes.
The electrodes were located along three concentric circles. The
distance from the well external ring was 3,6 and 7 meters. They were
dipped to the 41.0 - 43.0 meters height. The rectifiers were used as
power supply units for DC voltage. They had provided 74 V and 3300
A (Figure 4)

Figure 4

The controlled Deeping process was conducted in the following
way. First the ground was electrically treated with for 1.5 - 3.0 hours (voltage gradient was 0.2 V per sm, current density was about 2 A/
sq m. Then the well was gradually deepened. Previously the well had
been motionless for several Jays. (Figure 5)

For Southern waste treatment facilities the deeping well was
51.0 meter in diameter. The deeping height was 49.0 meters. Anodes
and cathodes were located on the knife part of the construction in
interchange order. The clay solution had the access to the electrodes.
As a result we had achieved deeping acceleration, bank correction
and eliminating of negative influence upon city building environment.

Perminov NA. Complete geotechnical and monitoring services for
the construction of the underground structure in a megapolis,
Proceedings of the International Geotechnical Conference,
Almaty. 2004;pp.361-366

Serebryakov DV. Of the study on vibrational process of soil
roadbed on the sections of the pairing of railway track with
bridges: Proceedings of international scientific conference
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Russia. 2015;240:pp.52-55.